Hi Chen-Yu, Sorry for the late reply. On 21/02/2017 05:55, Chen-Yu Tsai wrote: > On Wed, Feb 15, 2017 at 4:53 PM, Quentin Schulz > <quentin.schulz@xxxxxxxxxxxxxxxxxx> wrote: >> Hi, >> >> On 15/02/2017 01:46, Liam Breck wrote: >>> >>> On Tue, 14 Feb 2017 10:40:55 +0100 Quentin Schulz wrote: >>>> This adds the constant-charge-current property to the list of optional >>>> properties of the battery. >>>> >>>> The constant charge current is critical for batteries as they can't >>>> handle all charge currents. >>>> >>>> Signed-off-by: Quentin Schulz <quentin.schulz@xxxxxxxxxxxxxxxxxx> >>>> --- >>>> >>>> added in v3 >>>> >>>> Documentation/devicetree/bindings/power/supply/battery.txt | 2 ++ >>> >>> Is constant-charge-current dependent on the battery (e.g. capacity, nominal voltage, etc) or the >>> system (charger chip, input current/voltage, etc)? >>> >>> It belongs in Doc.../power/supply/battery.txt if it's a characteristic of the battery. >>> >>> Note, this page asserts that constant-current charging applies to NiMH batteries: >>> http://power-topics.blogspot.com/2016/05/constant-voltage-constant-current.html >>> >>> Related properties to be added to battery.txt near-future in a patchset for the BQ24190 >>> charger are as follows. These are not currently in enum power_supply_property, so the actual names >>> are still to be decided. >>> >>> precharge-current-microamp: >>> maximum charge current during precharge phase (typically 20% of battery capacity) >>> >>> termination-current-microamp (or endcharge-current): >>> a charge cycle terminates when the battery voltage is above recharge threshold, >>> and the current is below this setting (typically 10% of battery capacity) >>> >> >> We have a client with a board whose battery accepts a maximum of 300mA >> for charging. So depending on the battery, we cannot have any charging >> current we want. The AXP PmMICs set constant charge current in a range >> of 300mA-1800mA, so it is enforced by the charger but needs to be >> adapted depending on the battery present in the system. > > May I ask the capacity of the battery in question? > It is a 400mAh battery. Quentin > Typically one charges LiPo batteries at no more than 1C. So if it's > a 1800 mAh battery, the charge current should be no more than 1800 mA. > > ChenYu > >> The AXP PMICs charge battery with constant current (Ichrg) between the >> trickle voltage (Vtrkl which is ~3.0V) and the targeted voltage (Vtrgt; >> which seems to be the voltage telling the battery is fully charged). >> >> So if I understand correctly, "my" constant-charge-current would be >> located in the charging cycle between your precharge-current-microamp >> and the termination-current-microamp as it is the current for the >> charging process as a whole. >> >> See here[1] for the explanation in the datasheet (page 20). >> >> That would definitely match what is explained in your link for constant >> current. >> >> [1] http://dl.linux-sunxi.org/AXP/AXP209_Datasheet_v1.0en.pdf >> >> Let me know if something seems odd, >> Thanks, >> Quentin >> >> -- >> Quentin Schulz, Free Electrons >> Embedded Linux and Kernel engineering >> http://free-electrons.com > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- Quentin Schulz, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
